This invention relates to locks for preventing one member from sliding relative to another member. One of the members may for example be a patio door, a window or a cupboard door, with the other member being an associated frame member.
Many such locks are known, but there is still a need for an improved lock of this kind which is more effective than known locks but which nevertheless is relatively simple and not unduly expensive.
It is therefore an object of the invention to provide an improved lock of this kind.
According to the invention, a lock for preventing one member from moving relative to another member has a housing securable to one member and a plunger unit mounted in the housing. The plunger unit has a sleeve, a plunger slidably mounted in the sleeve, and a spring acting between the plunger and the sleeve to resiliently bias the plunger to a locking position in which a free end portion of the plunger projects from one end of the sleeve, the plunger also having a manually operable portion projecting from an opposite end of the sleeve. In the locking position, the free end portion of the plunger projects from the housing to extend into an aperture in the other member, when the housing is secured to said one member, and thereby prevent relative sliding movement between the members. The plunger also has an unlocking position in which the free end portion thereof is withdrawn from the aperture in the other member by pulling the manually operable portion against the action of the spring. The housing may include a main portion and a cover portion removably securable thereto, the main portion and the cover portion having longitudinally extending recesses receiving the plunger unit. The cover portion may be attachable to the main portion by sliding movement relative thereto, and the cover portion and the housing portion may have mutually engaging keyways to enable the sliding movement to be effected
The spring may be a helical spring which surrounds the plunger within the sleeve.
The manually operable portion and the free end portion of the plunger may be separate parts secured together by screw-threaded engagement, the separate parts being separable to enable the spring to be assembled with the plunger and the sleeve.
The sleeve and the housing may have inter-engaging means to prevent movement of the sleeve relative to the housing. A plurality of longitudinally-spaced inter-engaging means may be provided to enable the amount of projection of the free end portion of the plunger from the housing to be adjusted.
The manually operable portion of the plunger and the sleeve may have stop means which are mutually engageable by rotation of the manually operable portion of the plunger relative to the sleeve when the plunger is in its unlocking position to retain the plunger in the unlocking position.